Grand Slam Titles Problem

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+----------------+---------+
| Column Name    | Type    |
+----------------+---------+
| player_id      | int     |
| player_name    | varchar |
+----------------+---------+
player_id is the primary key for this table.
Each row in this table contains the name and the ID of a tennis player.

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+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| year          | int     |
| Wimbledon     | int     |
| Fr_open       | int     |
| US_open       | int     |
| Au_open       | int     |
+---------------+---------+
year is the primary key for this table.
Each row of this table containts the IDs of the players who won one each tennis tournament of the grand slam.

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Players table:
+-----------+-------------+
| player_id | player_name |
+-----------+-------------+
| 1         | Nadal       |
| 2         | Federer     |
| 3         | Novak       |
+-----------+-------------+

Championships table:
+------+-----------+---------+---------+---------+
| year | Wimbledon | Fr_open | US_open | Au_open |
+------+-----------+---------+---------+---------+
| 2018 | 1         | 1       | 1       | 1       |
| 2019 | 1         | 1       | 2       | 2       |
| 2020 | 2         | 1       | 2       | 2       |
+------+-----------+---------+---------+---------+

Result table:
+-----------+-------------+-------------------+
| player_id | player_name | grand_slams_count |
+-----------+-------------+-------------------+
| 2         | Federer     | 5                 |
| 1         | Nadal       | 7                 |
+-----------+-------------+-------------------+

Player 1 (Nadal) won 7 titles: Wimbledon (2018, 2019), Fr_open (2018, 2019, 2020), US_open (2018), and Au_open (2018).
Player 2 (Federer) won 5 titles: Wimbledon (2020), US_open (2019, 2020), and Au_open (2019, 2020).
Player 3 (Novak) did not win anything, we did not include them in the result table.

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select player_id, player_name,
	sum((if(Wimbledon = player_id,1,0) + 
		if(Fr_open = player_id,1,0) + 
		if(US_open = player_id,1,0) + 
		if(Au_open = player_id,1,0))) as grand_slams_count
from Players inner join Championships
on Wimbledon = player_id or Fr_open = player_id or US_open = player_id or Au_open = player_id
group by player_id